Connected component analysis method which can reuse label

ABSTRACT

A connected component analysis (CCA) method, which can use labels repeatedly, comprising: defining a label pattern comprising a label and a plurality of neighboring labels; setting a center label of a current pixel of a target binary image according to a binary value of the current pixel and the neighboring pixels; setting at least two of the neighboring labels according to whether the current pixel is in any one of a first row, a first column and a last column; and recording the center label to a label buffer. Labels for marking pixels of the target binary image are first center labels, and then are second center labels, and are the first center labels again after the labels are the second center labels.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a CCA (Connected Component Analysis) method, and particularly relates to a CCA method which can reuse labels and can replace labels in the label buffer when collisions occur.

2. Description of the Prior Art

Various CCA methods are described in prior arts to extract features from connected components (or named object, blob) from an input binary image. These features include area, bounding boxes and centroid. For real-time application, a fast (single pass without interrupting input streaming data flow) and efficient (minimal hardware resources) CCA design is crucial in hardware implementation. However, the CCA methods in prior art could not reuse labels, thus needs a large label buffer. Also, the CCA methods in prior art need a memory for storing translator, merger or collision table, for handling label collisions.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a CCA method which can reuse labels, and can handle label collision without increasing a size of the label buffer.

One embodiment of the present invention provides a connected component analysis (CCA) method, which can use labels repeatedly, comprising: defining a label pattern comprising a center label and a plurality of neighboring labels; setting a label of a current pixel of a target binary image according to a binary value of the current pixel and the neighboring pixels; setting at least two of the neighboring labels according to whether the current pixel is in any one of a first row, a first column and a last column; and recording the center label to a label buffer. Labels for marking pixels of the target binary image are first center labels, and then are second center labels, and are the first center labels again after the labels are the second center labels [We do not quite understand this sentence that was repeated throughout the document: Can you give us an example of the first center labels and second center labels].

The CCA method can further comprise: recording numbers respectively for different center labels [For the term “an image with specific binary value” mentioned throughout the document: Is this term referring to a blob within the target binary image? A blob within a target binary image refers to group of pixels that are connected with pixel value=1].

The CCA method can further comprise: recording centroid reference values for different center labels; computing a centroid of an image with a specific binary value according to the centroid reference values in the target binary image.

The CCA method can further comprise: recording bounding reference values for different center labels.

In view of above-mentioned embodiments, the label can be reused, and the label collision can be handled without increasing a size of the label buffer.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 -FIG. 4 are schematic diagrams illustrating a CCA method according to one embodiment of the present invention.

FIG. 5 -FIG. 10 are schematic diagrams illustrating examples of the CCA method illustrated in FIG. 1 -FIG. 4 .

FIG. 11 -FIG. 14 are schematic diagrams illustrating a CCA method according to one embodiment of the present invention.

FIG. 15 is a processing result of a binary image processed by the CCA method disclosed by the present invention.

DETAILED DESCRIPTION

Several embodiments are provided in following descriptions to explain the concept of the present invention. The method in following descriptions can be executed by programs stored in a non-transitory computer readable recording medium such as a hard disk, an optical disc or a memory. For example, the programs can be executed by a processing circuit. Additionally, the term “first”, “second”, “third” in following descriptions are only for the purpose of distinguishing different one elements, and do not mean the sequence of the elements.

FIG. 1 -FIG. 4 are schematic diagrams illustrating a CCA method according to one embodiment of the present invention. FIG. 1 -FIG. 4 correspond to the examples illustrated in FIG. 5 -FIG. 10 . which illustrates a 3×8 target binary image with 8-connectivity. Also, the embodiments illustrated in FIG. 1 -FIG. 4 uses a label pattern LP1 illustrated at upper right part of FIG. 1 . Lj in the label pattern LP1 means a label of a current pixel which is being processed, and can be named as a center label. La, Lb, Lc, Ld are neighboring labels which may be used to determine Lj. Specifically, La is a top left label of Lj, Lb is a top label of Lj, Lc is a top right label of Lj, and Ld is a left label of Lj.

Also, the value of Lj may be used to determine at least one of La, Lb, Lc, Ld. Furthermore, La, Lb, Lc, Ld may affect each other. Please note, the flows in FIG. 1 correspond to the label pattern LP1 and 3×8 target binary image with 8-connectivity. However, the flows can be varied correspond to the target binary image to be processed and different label patterns, based on the concept disclosed in FIG.1.

FIG. 1 comprises following steps:

Step 101

Start.

Step 102

Set

new_label=1

num_blob=0

Blob means the connected components.

Step 103

Set

P=a pixel value of the first pixel

Step 104

Set Collision=0

In one embodiment, collision means some specific neighboring labels have different values besides 0 [FIG.1: Arrow from 148 should be connected to 104, not 105].

Step 105

Determine if P=0, go to step 106_1 if the answer is no, and go to step 106_2 if the answer is yes [FIG. 1 : Arrow from 148 should be connected to 104, not 105].

Step 106_1

Determine if a current pixel is in a first row, go to step 107 if the answer is yes, and go to step 108 if the answer is no.

Step 106_2

Set Lj=0

Step 107

Set La=0, Lb=0, Lc=0

Step 108

Set Lb=Top label.

The top label means a top label of Lj stored in a label buffer [In FIG. 1 , the line connecting Step 108 to Step 109 is missing].

Step 109

Determine if the current pixel is in a first column, go to step 111 if the answer is yes, and go to step 110 if the answer is no.

Step 110

Determine if the current pixel is in a last column, go to step 112 if the answer is yes, and go to step 113 if the answer is no.

Step 111

Set La=0, Lc=Top right label, Ld=0

The top right label means a top right label of Lj stored in the label buffer.

Step 112

Set La=Top Left Label, Lc=0, Ld=Left Label

The top left label means a top left label of Lj stored in the label buffer.

The left label means a left label of Lj stored in the label buffer.

Step 113

Set La=Top Left Label, Lc=Top right label, Ld=Left Label

Step 114

Determine if La>0 and Lc>0, go to step 115 if the answer is yes, and go to step 118 if the answer is no.

Step 115

Determine if La=Lc, go to step 116 if the answer is yes, and go to step 117 if the answer is no.

FIG. 2 comprises following steps, which follow the steps illustrated in FIG. 1 :

Step 116

Set Lj=La

Step 117

Set

Collision=1

Lmin=min(La, Lc)

Lmax=max(La, Lc)

Step 118

Determine if Lc>0 and Ld>0, go to step 119 if the answer is yes, and go to step 122 if the answer is no.

Step 119

Determine if Lc=Ld, go to step 120 if the answer is yes, and go to step 121 if the answer is no.

Step 120

Set Lj=Lc

Step 121

Set Collision=1

Lmin=min(Lc, Ld)

Lmax=max(Lc, Ld)

Step 122

Determine if La, Lb, Lc and Ld are 0, go to step 123 if the answer is yes, and go to step 126 if the answer is no.

Step 123

Set

num_blob=num_blob+1

Lj=new_label new_label=num_label+1

Step 124

Determine if the new label (the new label set in step 123) is larger than a maximum label, go to step 125 if the answer is yes, and go to step 133 if the answer is no.

Step 125

Set the new label to be a value of a maximum label stored in the label buffer.

Step 126

Determine if La is larger than 0, go to step 127 if the answer is yes, and go to step 128 if the answer is no.

Step 127

Set Lj=La

Step 128

Determine if Lb is larger than 0, go to step 129 if the answer is yes, and go to step 130 if the answer is no.

Step 129

Set Lj=Lb

FIG. 3 , FIG. 4 comprises following steps, which follow the steps illustrated in FIG. 2 :

Step 130

Determine if Lc is larger than 0, go to step 131 if the answer is yes, and go to step 132 if the answer is no.

Step 131

Set Lj=Lc

Step 132

Set Lj=Ld

Step 133

Determine if Collision=1, go to step 134 if the answer is yes, and go to step 141 if the answer is no.

Step 134

Set Lj to Lmin

Step 135

Replace all Lmax in the label buffer to Lmin.

Lmax means the maximum label (s) of specific ones of neighboring labels, and Lmin means the minimum label(s) of specific ones of the neighboring labels.

Step 136

Replace all (new_label-1) in the label buffer with Lmax [FIG. 3 : The word “Replace” is missing].

For example, if the new_label is 2, than all labels 1 in the label buffer are replaced with Lmax.

Step 137

Set Featsize [Lmin]=FeatSize[Lmin]+FeatSize[Lmax]+1

Set Featsize [Lmax]=FeatSize [new label-1]

Set FeatSize [new label-1]=0

These steps are applied for computing numbers respectively for different center labels, to compute sizes for different center labels [Actually all the blobs within the target binary image are having the same binary value of “1”. The size computed here refer to the blobs size within the binary image, where each blob has its own label and size]. Other steps having FeatSize are for the same purpose.

Step 138

Set

FeatCent [Lmin]=FeatCent[Lmin]+FeatCent[Lmax]+[row, col] [FIG. 4 : FeatCent instead of FeatCen]

FeatCent [Lmax]=FeatCent [new_label-1]

FeatCent [new_label-1]=0 [row, col] means a row address and a column address of the current pixel.

These steps are applied for recording centroid reference values for different center labels [Similar comment for Step 137]. Other steps having FeatCent are for the same purpose.

Step 139

This step is used for recording bounding reference values for different center labels. Other steps having FeatBbox are for the same purpose.

Detail steps are as below:

Set

FeatBboxLeft[Lmin]=min(FeatBboxLeft[Lmin], FeatBboxLeft[Lmax], col)

FeatBboxRight[Lmin]=max(FeatBboxRight[Lmin], FeatBboxRight [Lmax], col)

FeatBboxTop[Lmin]=min(FeatBboxTop[Lmin], FeatBboxTop[Lmax], row)

FeatBboxBottom[Lmin]=min(FeatBboxBottom[Lmin], FeatBboxBottom[Lmax], row)

FeatBboxLeft[Lmax]=FeatBboxLeft[new_label-1]

FeatBboxRight[Lmax]=FeatBboxRight[new_label-1]

FeatBboxTop[Lmax]=FeatBboxTop[new_label-1]

FeatBboxBottom[Lmax]=FeatBboxBottom[new_label-1]

FeatBboxLeft[new_label-1]=0

FeatBboxRight[new_label-1]=0

FeatBboxTop[new_label-1]=0

FeatBboxBottom[new_label-1]=0

Step 140

Set

num_blob=num_blob-1

new_label=new_label-1

Step 141

Set

FeatSize[Lj]=FeatSize[Lj]+1

Step 142

Set

FeatCent[Lj]=FeatCent[Lj]+[row, col]

Step 143

Determine if FeatSize[Lj] is 1, go to step 146 if the answer is yes, and go to step 145 if the answer is no.

Step 144

Set

FeatBboxLeft[Lj]=col

FeatBboxRight[Lj]=col

FeatBboxTop[Lj]=row

FeatBboxBottom[Lj]=row

Step 145

Set

FeatBboxLeft[Lj]=min(FeatBboxLeft[Lj],col)

FeatBboxRight[Lj]=max(FeatBboxRight[Lj],col)

FeatBboxTop[Lj]=min(FeatBboxTop[Lj],row)

FeatBboxBottom[Lj]=max(FeatBboxBottom[Lj],row)

Step 146

Record Lj to label buffer

Step 147

Determine if the current pixel is the last pixel, go to step 149 if the answer is yes, and go to step 148 if the answer is no.

Step 148

Set P=a pixel value of a next pixel, and goes back to the step 104 to process next pixel.

Step 149

End

As stated above, FIG. 5 -FIG. 10 are schematic diagrams illustrating examples of the CCA method illustrated in FIG. 1 -FIG. 4 . In FIG. 5 -FIG. 10 , the binary input image means the target binary image, the label buffer is the above-mentioned label buffer, and the feature table (area) is for recording numbers respectively for different center labels [Similar comment for Step 137]. The feature table (Centroid) is for recording centroid reference values for different center labels. The feature table (Bounding Box) is for recording bounding reference values for different center labels. Also, (Rx,Cy) means a current pixel being processed is at a x-th row and a y-th column and a corresponding address of the label buffer.

The steps in FIG. 5 -FIG. 10 are stated as below. Please note, the results of these steps can be acquired following the flow illustrated in FIG. 1 -FIG. 4 , thus only brief descriptions thereof are provided.

FIG. 5 comprises following steps:

Step 1

The pixel at (R1, C1) has a pixel value of 0, thus Lj=0 and Lj is stored to the label buffer (R1, C1). It also means the pixel at (R1, C1) is marked by the center label 0.

Feature table (area) , the feature table (Centroid) and feature table (Bounding Box) are correspondingly set to be 0. For more detail, all feature tables value are reset or initialized to 0 for every new image, before the first pixel is processed. Therefore, in this steps, the pixel at (R1, C1) has a pixel value of 0, thus feature tables (already initialized to 0) will not be updated.

Step 2

(a) The pixel at (R1, C1) has a pixel value of 1.

The current pixel is in first row, thus La=Lb=Lc=0.

(b) The current pixel is not in a first column or a last column, La=Top Left Label=predetermine value=0, Lc=Top Right Label=predetermine value=0, Ld=left label=0.

In the step 2, Top Left Label and Top Right Label of the center label 1 do not exist, thus La, Lc are set to a predetermined value 0.

(c)Since La=Lb=Lc=0

Lj=new label=1, the new_label here is an initial new_label.

new_label=new_label+1=2

new_label is less than a max_label, so new_label=2. In this step, the max_label is an initial value 4, thus the new_label 2 is less than the max_label.

For more detail, the max_label refers to the maximum number of label and it depends on the memory size allocated for feature tables. Bigger max_label meaning bigger memory size is required to store more labels (1 label for each object/blob). For this particular target binary image example, max_label has to be set to minimally 4 in order to process the image correctly. Any new_label that is greater than 4 will be clipped to 4. By using max_label of 4 for this example, each feature table(size, centroid and bounding box) will be able to store information for up to 3 objects/blobs.

num_of_object=num_of_object+1=0+1=1

num_of_object is the num_of_blob in FIG. 1 -FIG. 4 .

(d)No collision occurs

Size[1]=Size[1]+1=1, the initial Size[1]=0. The Size[] means the FeatSize[] in the steps of FIG. 1 -FIG.4.

FeatCent[1]=FeatCent[1]+[1,2]=[1,2], the initial FeatCent[1]=0.

Size[1]=1, then

BboxLeft[1]=Col=2

BboxRight[1]=Col=2

BboxTop[1]=Row=1

BboxBottom[1]=Row=1

(e) Record Lj=1 to label buffer (R1, C1)

Step 3

(a) The pixel at (R1, C3) has a pixel value of 1.

The current pixel is in a first row, thus La=Lb=Lc=0.

(b) The current pixel is not in a first column or a last column, La=Top Left Label=predetermine value=0, Lc=Top Right Label=predetermine value=0, Ld=left label=1.

(c) Lj=Ld=1

(d)No collision occurs

Size[1]=Size[1]+1=2.

FeatCent[1]=FeatCent[1]+[1,3]=[1,2]+[1,3]=[2,5]

BboxLeft[1]=min(BboxLeft[1], col)=min(2,3)=2

BboxRight[1]=max(BboxRight[1], col)=max(2,3)=2

BboxTop[1]=min(BboxTop[1], row)=min(1,1)=1

BboxBottom[1]=max(Bboxbottom[1], row)=max(1,1)=1

(e) Record Lj=1 to label buffer (R1, C3)

Step 4

The pixel at (R1, C4) has a pixel value of 0, thus Lj=0 and Lj is stored to the label buffer (R1, C4). Feature table (area), the feature table (Centroid) and feature table (Bounding Box) are not changed.

FIG. 6 comprises following steps:

Step 5

The pixel at (R1, C5) has a pixel value of 0, thus Lj=0 and Lj is stored to the label buffer (R1, C5). Feature table (area), the feature table (Centroid) and feature table (Bounding Box) are not changed.

Step 6

(a) The pixel at (R1, C6) has a pixel value of 1.

The current pixel is in first row, thus La=Lb=Lc=0.

(b) The current pixel is not in a first column or a last column, La=Top Left Label=predetermine value=0, Lc=Top Right Label=predetermine value=0, Ld=left label=Label buffer (R1,C6)=0.

(c)Since La=Lb=Lc=0

Lj=new_label=2

new_label=new_label+1=2+1=3

new_label is less than a max_label, so new label=3

num_of_object=num_of_object+1=1+1=2

(d)No collision occurs

Size[2]=Size[2]+1=1, the initial Size[2]=0.

FeatCent[2]=FeatCent[2]+[1,6]=[1,6], the initial FeatCent[2]=0.

Size[2]=1, then

BboxLeft[2]=Col=6

BboxRight[2]=Col=6

BboxTop[2]=Row=1

BboxBottom[2]=Row=1

(e) Record Lj=2 to label buffer (R1, C6)

Step 7

The pixel at (R1, C7) has a pixel value of 0, thus Lj=0 and Lj is stored to the label buffer (R1, C7). Feature table (area), the feature table (Centroid) and feature table (Bounding Box) are not changed.

Step 8

(a) The pixel at (R1, C8) has a pixel value of 1.

The current pixel is in a first row, thus La=Lb=Lc=0.

(b) The current pixel is in a last column, La=Top Left Label=predetermine value=0, Lc=0, Ld=left label=Label buffer (R1, C7) =0.

(c)Since La=Lb=Lc=Ld=0

Lj=new_label=3

new_label=new_label+1=3+1=4

new_label is less than a max_label, so new_label=4 [Same comment for Step 2 (c) above]

num_of_object=num_of_object+1=2+1=3

(d)No collision occurs

Size[3]=Size[3]+1=1, the initial Size[3]=0.

FeatCent[3]=FeatCent[3]+[1,8]=[1,8]. The initial FeatCent[3]=0.

Size[3]=1, then

BboxLeft[2]=Col=8

BboxRight[2]=Col=8

BboxTop[2]=Row=1

BboxBottom[2]=Row=1

(e) Record Lj=3 to label buffer (R1, C8)

FIG.7 comprises following steps:

Step 9

(a) The pixel at (R2, Cl) has a pixel value of 1.

Lb=Top label=Label buffer (R1, C1)=0.

(b) The current pixel is not in a first row but in a first column, thus La=O, Lc=Top Right label=Label buffer (R1, C1)=1, Ld=0.

(c) Lc>0, Lj=Lc=1

(d)No collision occurs

Size[1]=Size[1]+2=3

FeatCent[1]=FeatCent[1]+[2,1]=[2,5]+[2,1]=[4,6].

BboxLeft[1]=min(BboxLeft[1], col)=min(2,1)=1

BboxRight[1]=max(BboxRight[1], col)=max(3,1)=3

BboxTop[1]=min(BboxTop[1], row)=min(1,2)=1

BboxBottom[1]=max(Bboxbottom[1], row)=max(1,2)=2

(e) Record Lj=1 to label buffer (R2, Cl)

Step 10

(a) The pixel at (R2, C2) has a pixel value of 1.

Lb=Top label=Label buffer (R1, C1)=1.

(b) The current pixel is not in first row and not in first column, thus La=Top Left label=Label buffer (R1, C1)=0, Lc=Top Right label=Label buffer (R1, C3)=1, Ld=Left label=Label buffer (R2, C1)=1.

(c) Lc>0 and Ld>0, and Lc=Ld

Lj=Lc=1

(d)No collision occurs

Size[1]=Size[1]+1=3+1=4

FeatCent[1]=FeatCent[1]+[2,2]=[4,6]+[2,2]=[6,8].

BboxLeft[1]=min(BboxLeft[1], col)=min(1,2)=1

BboxRight[1]=max(BboxRight[1], col)=max(3,2)=3

BboxTop[1]=min(BboxTop[1], row)=min(1,2)=1

BboxBottom[1]=max(Bboxbottom[1], row)=max(2,2)=2

(e) Record Lj=1 to label buffer (R2, C2)

Step 11

(a) The pixel at (R2, C3) has a pixel value of 1.

Lb=Top label=Label buffer (R1, C3)=1.

(b) The current pixel is not in first row and not in first column, thus La=Top Left label=Label buffer (R1, C1)=1, Lc=Top Right label=Label buffer (R1, C4)=0, Ld=Left label=Label buffer (R2, C2)=1.

(c) La>0

Lj=La=1

(d)No collision occurs

Size[1]=Size[1]+1=4+1=5

FeatCent[1]=FeatCent[1]+[2,3]=[6,8]+[2,3]=[8,11].

BboxLeft[1]=min(BboxLeft[1], col)=min(1,3)=1

BboxRight[1]=max(BboxRight[1], col)=max(3,3)=3

BboxTop[1]=min(BboxTop[1], row)=min(1,2)=1

BboxBottom[1]=max(Bboxbottom[1], row)=max(2,2)=2

(e) Record Lj=1 to label buffer (R2, C3)

Please note, in the embodiment of FIG. 5 -FIG. 10 . the size of the label buffer is a number of column+1, thus is 9.

Therefore, from step 11, the previously recorded labels are removed such that the label buffer stores only 9 labels.

Step 12

The rules of step 12 are similar with which of step 11, thus are omitted for brevity here.

FIG. 8 comprises following steps:

Step 13

The rules of step 13 are similar with which of the step 4, thus are omitted for brevity here.

Step 14

(a) The pixel at (R2, C6) has a pixel value of 1.

Lb=Top label=Label buffer (R1, C6)=2.

(b) The current pixel is not in first row and not in first column, thus La=Top Left label=Label buffer (R1, C5)=0, Lc=Top Right label=Label buffer (R1, C7)=0, Ld=Left label=Label buffer (R2, C5)=0.

(c) Lb>0

Lj=Lb=2

(d)No collision occurs

Size[2]=Size[2]+1=1+1=2

FeatCent[2]=FeatCent[2]+[2,6]=[1,6]+[2,6]=[3,12].

BboxLeft[2]=min(BboxLeft[2], col)=min(6,6)=6

BboxRight[2]=max(BboxRight[2], col)=max(6,6)=6

BboxTop[2]=min(BboxTop[2], row)=min(1,2)=1

BboxBottom[2]=max(Bboxbottom[2], row)=max(1,2)=2

(e) Record Lj=2 to label buffer (R2, C6)

Step 15

The rules of step 15 are similar with which of the step 4, thus are omitted for brevity here.

Step 16

(a) The pixel at (R2, C8) has a pixel value of 1.

Lb=Top label=Label buffer (R1, C8)=3.

(b) The current pixel is not in first row and is in a last column, thus La=Top Left label=Label buffer (R1, C7)=0, Lc=0, Ld=Left label=Label buffer (R2, C7)=0.

(c) Lb>0

Lj=Lb=3

(d)No collision occurs

Size[3]=Size[3]+1=1+1=2

FeatCent[3]=FeatCent[3]+[2,8]=[1,8]+[2,8]=[3,16].

BboxLeft[3]=min(BboxLeft[3], col)=min(8,8)=8

BboxRight[3]=max(BboxRight[3], col)=max(8,8)=8

BboxTop[3]=min(BboxTop[3], row)=min(1,2)=1

BboxBottom[3]=max(Bboxbottom[3], row)=max(1,2)=2

(e) Record Lj=3 to label buffer (R2, C8)

FIG.9 comprises following steps:

Step 17

The rules of step 17 are similar with which of the step 1, thus are omitted for brevity here.

Step 18

(a) The pixel at (R3, C2) has a pixel value of 1.

Lb=Top label=Label buffer (R2, C2)=1.

(b) The current pixel is not in first row and not in first column, thus La=Top Left label=Label buffer (R2, C1)=1, Lc=Top Right label=Label buffer (R2, C3)=1, Ld=Left label=Label buffer (R3, C1)=0.

(c) La>0, Lc>0, La=Lc

Lj=La=1

(d)No collision occurs

Size[1]=Size[1]+1=6+1=7

FeatCent[1]=FeatCent[1]+[3,2]=[10,15]+[3,2]=[13,17].

BboxLeft[1]=min(BboxLeft[1], col)=min(1,2)=1

BboxRight[1]=max(BboxRight[1], col)=max(4,2)=4

BboxTop[1]=min(BboxTop[1], row)=min(1,3)=1

BboxBottom[1]=max(Bboxbottom[1], row)=max(2,3)=3

(e) Record Lj=1 to label buffer (R3, C2)

Step 19

The rules of step 19 are similar with which of the step 18, thus are omitted for brevity here.

Step 20

The rules of step 20 are similar with which of the step 18, thus are omitted for brevity here.

In the steps 1-20, the center label Lj gradually increases but is less than the maximum label. Specifically, the center label Lj gradually increases from 1 to 3 but is less than 4.

FIG. 10 comprises following steps:

Step 21

(a) The pixel at (R3, C5) has a pixel value of 1.

Lb=Top label=Label buffer (R2, C5)=0.

(b) The current pixel is not in first row and not in first column, thus La=Top Left label=Label buffer (R2, C4)=1, Lc=Top Right label=Label buffer (R2, C6)=2, Ld=Left label=Label buffer (R3, C4)=1.

(c)Lc>0, Ld>0, but Lc, Ld are different

Collision=1

Lmin=min(Lc, Ld)=1

Lmax=max(Lc,Ld)=2

(d) Collision exists

(i) Lj=Lmin=1

(ii) Replace Lmax in the label buffer with Lmin

(iii)Replace label=new_label-1 or label=3 in label buffer with

Lmax or 2.

(iv)Size[Lmin]=Size[Lmin]+Size[Lmax]+1

→Size[1]+Size[2]+1=9+2+1=12

Size[Lmax]=Size[new_label-1]→22 Size[2]=Size[3]=2

Size [new_label-1]=0→Size [3]=0

(v)FeatCent[Lmin]=FeatCent[Lmin]+FeatCent[Lmax]+[3,5]

→FeatCent[1]+FeatCent[2]+[3,5]

→[19,24]+[3,12] +[3,5]=[25,41]

FeatCent [Lmax]=FeatCent [new_label-1]

→FeatCent [2]=FeatCent [3]=[3,16]

FeatCent [new_label-1]=04 FeatCent [3]=0

(Vi)

FeatBboxLeft[Lmin]=

min(FeatBboxLeft[Lmin], FeatBboxLeft[Lmax], col)

→FeatBboxLeft[1]=min(1,6,5)=1

FeatBboxRight[Lmin]=

max(FeatBboxRight[Lmin], FeatBboxRight [Lmax], col)

→FeatBboxRight[1]=max[4,6,5]=6

FeatBboxTop[Lmin]=

min(FeatBboxTop[Lmin], FeatBboxTop[Lmax], row)

→FeatBboxTop[1]=min[1,1,3]=1

FeatBboxBottom[Lmin]=

min(FeatBboxBottom[Lmin], FeatBboxBottom[Lmax], row)

→FeatBboxBottom[l]=max(3,2,3)=3

FeatBboxLeft[Lmax]=FeatBboxLeft[new_label-1]

→FeatBboxLeft[2]=FeatBboxLeft[3]=8

FeatBboxRight[Lmax]=FeatBboxRight[new_label-1]

→FeatBboxRight[2]=FeatBboxRight[3]=8

FeatBboxTop[Lmax]=FeatBboxTop[new_label-1]

→FeatBboxTop[2]=FeatBboxTop[3]=1

FeatBboxBottom[Lmax]=FeatBboxBottom[new_label-1]

→FeatBboxBottom[2]=FeatBboxBottom [3]=2

FeatBboxLeft[new_label-1]=0→

FeatBboxLeft[3]=0

FeatBboxRight[new_label-1]=0→

FeatBboxRight[3]=0

FeatBboxTop[new_label-1]=0→

FeatBboxTop[3]=0

FeatBboxBottom[new_label-1]=0→

BeatBboxBottom[3]=0

(vii)

new_label=new_label-1=4-1=3

(viii)

num_of_object=number_of_object-1=3-1=2

(ix)

(e) Record Lj=1 to label buffer (R3, C5)

In the step 21, the pixel which is marked by the label 3 is changed to the label 1, thus the Feature Table (Area), Feature Table (Centroid) and the Feature Table (Bounding Box) are correspondingly changed. Therefore, in the step 21, the label 1 is reused.

Step 22

(a) The pixel at (R3, C6) has a pixel value of 1.

Lb=Top label=Label buffer (R2, C6)=1.

(b) The current pixel is not in first row and not in first column, thus La=Top Left label=Label buffer (R2, C5)=0, Lc=Top Right label=Label buffer (R2, C7)=0, Ld=Left label=Label buffer (R3, C5)=1.

(c) Lb>0

Lj=Lb=1

(d)No collision occurs

Size[1]=Size[1]+1=1+1=2

FeatCent[1]=FeatCent[1]+[3,6]=[25,41]+[3,6]=[28,47].

BboxLeft[1]=min(BboxLeft[1], col)=min(1,6)=1

BboxRight[1]=max(BboxRight[1], col)=max(6,6)=6

BboxTop[1]=min(BboxTop[1], row)=min(1,3)=1

BboxBottom[1]=max(Bboxbottom[1], row)=max(3,3)=3

(e) Record Lj=1 to label buffer (R3, C6)

Step 23

(a) The pixel at (R3, C7) has a pixel value of 1.

Lb=Top label=Label buffer (R2, C7)=0.

(b) The current pixel is not in first row and not in first column, thus La=Top Left label=Label buffer (R2, C6)=1, Lc=Top Right label=Label buffer (R2, C8)=2, Ld=Left label=Label buffer (R3, C6)=1.

(c)La>0, Lc>0, but La, Lc are different

Collision=1

Lmin=min(Lc, Ld)=1

Lmax=max (Lc, Ld) =2

(d) Collision exists

(i) Lj=Lmin=1

(ii) Replace Lmax in the label buffer with Lmin

(iii)Replace label=new_label-1 or label=2 in label buffer with

Lmax or 2.

(iv)Size[Lmin]=Size[Lmin]+Size[Lmax]+1

→Size[1]+Size[2]+1=13+2+1=16

Size[Lmax]=Size[new_label-1]→Size[2]=2

Size [new_label-1]=0→ Size [2]=0

(v)FeatCent[Lmin]=FeatCent[Lmin]+FeatCent[Lmax]+[3,7]

FeatCent[1]+FeatCent[2]+[3,7]

→[28,47]+[3,16] +[3,7]=[34,70]

FeatCent [Lmax]=FeatCent [new_label-1]

→FeatCent [2]=FeatCent [3]=[3,16]

FeatCent [new_label-1]=0 →FeatCent [2]=0

(Vi)

FeatBboxLeft[Lmin]=

min(FeatBboxLeft[Lmin], FeatBboxLeft[Lmax], col)

→FeatBboxLeft[1]=min(1,8,7)=1

FeatBboxRight[Lmin]=

max(FeatBboxRight[Lmin], FeatBboxRight [Lmax], col)

→FeatBboxRight[1]=max[6,8,7]=8

FeatBboxTop[Lmin]=

min(FeatBboxTop[Lmin], FeatBboxTop[Lmax], row)

→FeatBboxTop[1]=min[1,1,3]=1

FeatBboxBottom[Lmin]=min(FeatBboxBottom[Lmin], FeatBboxBottom[Lmax], row)

→FeatBboxBottom[1]=max(3,2,3)=3

FeatBboxLeft[Lmax]=FeatBboxLeft[new_label-1]

→FeatBboxLeft [2 ] =8

FeatBboxRight[Lmax]=FeatBboxRight[new_label-1]

→FeatBboxRight[2]=8

FeatBboxTop[Lmax]=FeatBboxTop[new_label-1]

→FeatBboxTop[2]=1

FeatBboxBottom[Lmax]=FeatBboxBottom[new_label-1]

→FeatBboxBottom[2]=2

FeatBboxLeft[new_label-l]=0→

FeatBboxLeft[2]=0

FeatBboxRight[new_label-l]=0→

FeatBboxRight[2]=0

FeatBboxTop[new_label-1]=0→

FeatBboxTop[2]=0

FeatBboxBottom[new_label-1]=0→

BeatBboxBottom[2]=0

(vii)

new_label=new_label-1=3-1=2

(viii)

num_of_object=number_of_object-1=2-1=1

(xi)

(e) Record Lj=1 to label buffer (R3, C7)

In the step 23, the pixel which is marked by the label 2 is changed to the label 1, thus the Feature Table (Area), Feature Table (Centroid) and the Feature Table (Bounding Box) are correspondingly changed.

Step 24

(a) The pixel at (R3, C8) has a pixel value of 1.

Lb=Top label=Label buffer (R2, C8)=1.

(b) The current pixel is not in first row and is in a last column, thus La=Top Left label=Label buffer (R2, C7)=0, Lc=0, Ld=Left label=Label buffer (R3, C7)=1.

(c) Lb>0

Lj=Lb=1

(d)No collision occurs

Size[1]=Size[1]+1=16+1=17

FeatCent[1]=FeatCent[1]+[3,8]=[34,70]+[3,8]=[37,78].

BboxLeft[1]=min(BboxLeft[1], col)=min(1,8)=1

BboxRight[1]=max(BboxRight[1], col)=max(8,8)=8

BboxTop[1]=min(BboxTop[1], row)=min(1,3)=1

BboxBottom[1]=max(Bboxbottom[1], row)=max(3,3)=3

(e) Record Lj=1 to label buffer (R3, C8)

In the step 24, all labels are changed to 1, and the process ends since (R3, C8) is the final pixel.

Please note, in the above steps, the centroid coordinate [row,column] for the object can be computed by dividing FeatCent by FeatSize. For example, in the step 24, the centroid coordinate [row,column] for the object can be shown as

Centroid[row, column] = FeatCent/FeatSize = [37, 78]/17 = [2.18, 4.58]

[Actual coordinate [row,column] for each blob can be computed by dividing FeatCent by FeatSize as shown below:

Centroid[row, column] = FeatCent/FeatSize = [37, 78]/17 = [2.18, 4.58]

A CCA method disclosed by above mentions embodiments can be summarized to have following steps:

defining a label pattern comprising a center label and a plurality of neighboring labels (e.g., the first label pattern LP1);

setting a label of a current pixel of a target binary image according to a binary value of the current pixel and the neighboring pixels (e.g., steps 103-120 in FIG. 1 and FIG. 2 );

setting at least two of the neighboring labels according to whether the current pixel is in any one of a first row, a first column and a last column(e.g., steps 106_1, 119,110 in FIG. 1 ); and

recording the center label to a label buffer;

wherein labels for marking pixels of the target binary image are first center labels, and then are second center labels, and are the first center labels again after the labels are the second center labels (e.g., pixel (R1, C1) is marked by 1 in the step 2, and then pixel (R1, C6) is marked by 2 in the step 6, and the pixel (R3, C6) is marked by 1 again in the step 22 [Same as the first comment at page 3 where we do not quite understand the first center labels and second center labels. Besides, the example for step 21 mentioned above, pixel (R2, C7) is actually 0, and (R2, C8)=1. Are these typo?].

The CCA method can further comprises at least one of following steps:

Set the center label to a new value if all of the neighboring labels are 0 (e.g., steps 122, 123 in FIG. 1 ).

Set the center label to the new value plus 1, if all of the neighboring labels are 0 again in a process of a next pixel (e.g., steps 123 in FIG. 2 ).

Set the center label to be a corresponding one of the neighboring labels if the corresponding one of the neighboring labels is larger than 0 (e.g., steps 126-129 in FIG. 2 ).

Limit the center label to be lower than a maximum label threshold (e.g., steps 124, 125 in FIG. 2 ).

Set the center label according to whether collision of used labels occurs (e.g., step 133 in FIG. 3 ).

center label is set to a minimum one of specific ones of the neighboring labels when the collision occurs(e.g., step 134 in FIG. 3 ) .

Replace the center labels recorded in the label buffer with other values according to whether collision of used labels occurs (e.g., steps 135, 136 in FIG. 3 ).

At least maximum one of specific ones of the neighboring labels is set to a minimum one of specific ones of the neighboring labels when the collision occurs (e.g., step 135 in FIG. 3 ).

Set the center label to a new value if all of the neighboring labels are 0.

The center label which is recorded in the label buffer and has a value of the new value minus one, is replaced by a maximum one of the center labels of specific ones of the neighboring labels when the collision of used labels occurs (e.g., step 136 in FIG. 3 ).

Besides the above-mentioned steps for computing the center label Lj, the CCA method can further comprise a step of recording numbers respectively for different center labels to compute a size of an image with a specific binary value in the target binary image (e.g, the Feature Table (Area) in FIG. 5 -FIG. 10 ). Such step can be implemented by computing size information related with a minimum one of specific ones of the neighboring labels, a maximum one of specific ones of the neighboring labels, and a new label, to compute the size (e.g., step 137 in FIG. 3 ).

Also, the CCA method can further comprise a step of recording centroid reference values for different center labels; computing a centroid of an image with a specific binary value according to the centroid reference values in the target binary image. (e.g, the Feature Table (Centroid) in FIG. 5 -FIG. 10 ). Such step can be implemented by computing centroid information related with a minimum one of specific ones of the neighboring labels, a maximum one of specific ones of the neighboring labels, and a new label, to compute the centroid (e.g., step 138 in FIG. 4 ).

Additionally, the CCA method can further comprise a step of recording bounding reference values for different center labels; computing a bounding box of an image with a specific binary value according to the bounding reference values in the target binary image. Such step can be implemented by computing bounding information related with a minimum one of specific ones of the neighboring labels, a maximum one of specific ones of the neighboring labels, and a new label, to compute the bounding box (e.g., step 139 in FIG. 4 ).

The above-mentioned rules and steps can be applied for other label patterns and target binary image. FIG. 11 -FIG. 14 are schematic diagrams illustrating a CCA method according to one embodiment of the present invention. In FIG. 11 -FIG. 14 , a second label pattern LP2 is used, which comprises a center label Lj, and neighboring labels Lb, Ld. FIG. 11 -FIG. 14 comprise following steps:

Step 1101

Start.

Step 1102

Set

new_label=1

num_blob=0

Step 1103

Set

P=a pixel value of the first pixel

Step 1104

Set Collision=0

Step 1105

Determine if P=0.

Step 1106

Set Lj=0

Step 1107

Determine if a current pixel is in a first row.

Step 1108

Set Lb=0

Step 1109

Set Lb=Top label.

Step 1110

Determine if the current pixel is in a first column

Step 1111

Set Ld=0

Step 1112

Set Ld=Left Label

FIG.12 comprises following steps, which follow the steps illustrated in FIG.11:

Step 1113

Determine if Lb=0 and Ld=0.

Step 1114

Set

num_blob=num_blob+1

Lj=new label

new_label=num_label+1

Step 1115

Determine if the new label (the new label set in step 1114) is larger than a maximum label.

Step 1116

Set the new label to be a maximum label stored in the label buffer.

Step 1117

Determine if Lb>0 and Ld=0.

Step 1118

Set Lj=Lb

Step 1119

Determine if Lb=0 and Ld>0.

Step 1120

Set Lj=Ld

Step 1121

Determine if Lb=Ld.

Step 1118

Set Lj=Lb

Step 1123

Set

Collision=1

Lmin=min(Lb, Ld)

Lmax=max(Lb, Ld)

Step 1124

Determine if Collision=1.

Step 1125

Set

FeatSize[Lj]=FeatSize[Lj]+1

Step 1126

Set Lj to Lmin

Step 1127

Replace all Lmax in the label buffer to Lmin.

Step 1128

Replace all (new_label-1) in the label buffer with Lmax.

Step 1129

Set Featsize [Lmin]=FeatSize[Lmin]+FeatSize[Lmax]+1

Set Featsize [Lmax]=FeatSize [new_label-1]

Set FeatSize [new_label-1]=0

Step 1130

Set

FeatCent [Lmin]=FeatCent[Lmin]+FeatCent[Lmax]+[row, col]

[FIG.13: Should be FeatCent instead of FeatCen]

FeatCent [Lmax]=FeatCent [new_label-1]

FeatCent [new label-1]=0

Step 1131

Set

FeatBboxLeft[Lmin]=

min(FeatBboxLeft[Lmin], FeatBboxLeft[Lmax], col)

FeatBboxRight[Lmin]=

max(FeatBboxRight[Lmin], FeatBboxRight [Lmax], col)

FeatBboxTop[Lmin]=

min(FeatBboxTop[Lmin], FeatBboxTop[Lmax], row)

FeatBboxBottom[Lmin]=

min(FeatBboxBottom[Lmin], FeatBboxBottom[Lmax], row)

FeatBboxLeft[Lmax]=FeatBboxLeft[new_label-1]

FeatBboxRight[Lmax]=FeatBboxRight[new_label-1]

FeatBboxTop[Lmax]=FeatBboxTop[new_label-1]

FeatBboxBottom[Lmax]=FeatBboxBottom[new_label-1]

FeatBboxLeft[new_label-1]=0

FeatBboxRight[new_label-1]=0

FeatBboxTop[new_label-1]=0

FeatBboxBottom[new_label-1]=0

[FIG. 13 : Step 1131 should be connected to Step 1136]

Step 1132

Set

FeatCent[Lj]=FeatCent[Lj]+[row, col]

Step 1133

Determine if FeatSize[Lj] is 1.

[FIG. 13 : Should be 1133 instead of 1132]

Step 1134

Set

FeatBboxLeft[Lj]=col

FeatBboxRight[Lj]=col

FeatBboxTop[Lj]=row

FeatBboxBottom[Lj]=row

[FIG.13: Should be 1134 instead of 1132]

Step 1135

Set

FeatBboxLeft[Lj]=min(FeatBboxLeft[Lj],col)

FeatBboxRight[Lj]=max(FeatBboxRight[Lj],col)

FeatBboxTop[Lj]=min(FeatBboxTop[Lj],row)

FeatBboxBottom[Lj]=max(FeatBboxBottom[Lj],row)

Step 1136

num_blob=num_blob-1

new_label=new_label-1

Step 1137

Record Lj to label buffer

Step 1138

Determine if the current pixel is the last pixel.

Step 1139

Set P=a pixel value of a next pixel, and goes back to the step 1104 to process next pixel. [FIG. 11 : From Step 1139 to Step 1104, but arrow is pointing to Step 1105]

Step 1140

End

The meanings of all steps in FIG. 11 -FIG. 14 are clearly defined in steps of FIG. 1 -FIG. 10 , thus are no longer repeated here.

FIG. 15 is a processing result of a binary image processed by the CCA method disclosed by the present invention. In this example, objects in the binary image 1500 are identified and minimally labeled. In other words, minimum labels are used to label the objects. For example, the object Obl is labeled by 1, the object Ob2 is labeled by 2 . . . and so on.

The CCA method can be applied to an image sensor comprising a sensor array (e.g., a pixel array) and a processing circuit. In such case, the sensor array outputs a binary image, wherein the binary image has M*N pixels, M>2 and N>3, such as the binary image 1500 in FIG. 15 . The processing circuit receives the binary image and processes the binary image to identify at least one object in the binary image through minimally labeling at least one object. If the number of the object units (e.g., a pixel image) of the object is X, the number of a corresponding label is X. For example, the object Obl with 18 object units is labeled by 1 and the number of label 1 is 18. For another example, the object Ob 2 with 32 object units is labeled by 2 and the number of label 2 is 32. In other words, a number of the label and a number of the object units which is labeled by the label are identical.

In view of above-mentioned embodiments, the label can be reused, and the label collision can be handled without increasing a size of the label buffer.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. A connected component analysis method, which can use labels repeatedly, comprising: defining a label pattern comprising a center label and a plurality of neighboring labels; setting a label of a current pixel of a target binary image according to a binary value of the current pixel and the neighboring pixels; setting at least two of the neighboring labels according to whether the current pixel is in any one of a first row, a first column and a last column; and recording the center label to a label buffer; wherein labels for marking pixels of the target binary image are first center labels, and then are second center labels, and are the first center labels again after the labels are the second center labels.
 2. The connected component analysis method of claim 1, further comprising: setting the center label to a new value if all of the neighboring labels are
 0. 3. The connected component analysis method of claim 2, further comprising: setting the center label to the new value plus 1, if all of the neighboring labels are 0 again in a process of a next pixel.
 4. The connected component analysis method of claim 1, further comprising: setting the center label to be a corresponding one of the neighboring labels if the corresponding one of the neighboring labels is larger than
 0. 5. The connected component analysis method of claim 1, further comprising: limiting the center label to be lower than a maximum label threshold.
 6. The connected component analysis method of claim 1, further comprising: setting the center label according to whether collision of used labels occurs, wherein the collision means some specific ones of the neighboring labels are notO and are different.
 7. The connected component analysis method of claim 6, wherein the center label is set to a minimum one of specific ones of the neighboring labels when the collision occurs.
 8. The connected component analysis method of claim 1, further comprising: replacing the center labels recorded in the label buffer with other values according to whether collision of used labels occurs.
 9. The connected component analysis method of claim 8, wherein at least maximum one of specific ones of the neighboring labels is set to a minimum one of the specific ones of the neighboring labels when the collision occurs.
 10. The connected component analysis method of claim 8, further comprising: setting the center label to a new value if all of the neighboring labels are 0; wherein the center label which is recorded in the label buffer and has a value of the new value minus one, is replaced by a maximum one of the specific ones of the neighboring labels when the collision of used labels occurs.
 11. The connected component analysis method of claim 1, further comprising: recording numbers respectively for different ones of the center labels.
 12. The connected component analysis method of claim 11, further comprising: computing size information related with a minimum one of specific ones of the neighboring labels, a maximum one of the specific ones of the neighboring labels, and a new label, to compute the size.
 13. The connected component analysis method of claim 1, further comprising: recording centroid reference values for different center labels.
 14. The connected component analysis method of claim 13, further comprising: computing centroid information related with a minimum one of specific ones of the neighboring labels, a maximum one of the specific ones of the neighboring labels, and a new label, to compute the centroid.
 15. The connected component analysis method of claim 1, further comprising: recording bounding reference values for different ones of the center labels.
 16. The connected component analysis method of claim 15, further comprising: computing bounding information related with a minimum one of specific ones of the neighboring labels, a maximum one of the specific ones of the neighboring labels, and a new label, to compute the bounding box.
 17. The connected component analysis method of claim 1, wherein a number of bits that the label buffer can record is a number of columns of the target binary image plus
 1. 18. An image sensor, comprising: a sensor array, outputting a binary image, wherein the binary image has M*N pixels, M>2 and N>3; and a processing circuit, receiving the binary image and processing the binary image to identify at least one object in the binary image through minimally labeling at least one object unit, wherein if the number of the least one object unit is X, the number of a corresponding label is X. 